1. Field of the Invention
The present invention relates to a wavelength conversion member, a backlight unit including the wavelength conversion member, a liquid crystal display device, and a method of manufacturing a wavelength conversion member, the wavelength conversion member including a wavelength conversion layer including quantum dots which emit fluorescence when irradiated with excitation light.
2. Description of the Related Art
A flat panel display such as a liquid crystal display device (hereinafter, also referred to as “LCD”) has been more widely used as a space-saving image display device having low power consumption. A liquid crystal display device includes at least a backlight and a liquid crystal cell and typically further includes a member such as a backlight-side polarizing plate or a visible-side polarizing plate.
Recently, a configuration in which a wavelength conversion layer including quantum dots (QDs) as a light emitting material is provided in a wavelength conversion member of a backlight unit in order to improve color reproducibility of a LCD has attracted attention (refer to US2012/0113672A). The wavelength conversion member converts the wavelength of light incident from a light source so as to emit white light. In the wavelength conversion layer including the quantum dots as a light emitting material, white light can be realized using fluorescence which is emitted by excitation of two or three kinds of quantum dots having different light emitting properties caused by light incident from a light source.
The fluorescence emitted from the quantum dots has high brightness and a small full width at half maximum. Therefore, a LCD using quantum dots has excellent color reproducibility. Due to the progress of such a three-wavelength light source technique using quantum dots, the color reproduction range has been widened from 72% to 100% in terms of National Television System Committee (NTSC) ratio.
Quantum dots have a problem in that the emission intensity decreases due to a photooxidation reaction when coming into contact with oxygen. Regarding this point, JP2014-523634A reports a wavelength conversion member in which quantum dots are embedded in an acrylic resin having excellent heat resistance and oxygen barrier properties in order to protect the quantum dots from oxygen and the like.